Minimally invasive surgery (MIS) generally refers to the use of laparoscopy in addition to other techniques that reduce trauma by limiting the size of the operative incision. Application of these concepts has led to an overall reduction in post-operative pain, improved recovery, and decreased utilization of medical resources in the perioperative period of many operations. Furthermore, as the physiologic state appears to be less altered following MIS, the establishment of fast-track protocols have enabled patients to meet the criteria for discharge from the hospital significantly sooner due to improved recuperation of bowel function following abdominal surgery.
From a purely technical standpoint, laparoscopic surgery also provides certain advantages over open surgery. In the abdomen or pelvis, carbon dioxide gas is used to insufflate the abdomen in order to expand the working space within the peritoneal cavity and provide exposure of the operative field. At times, the visualization provided by the laparoscope is far superior to that seen by the surgeon in a traditionally open operation. Dissection of fine tissues can be performed meticulously while inspecting the structures of interest at a very near distance. This is especially true in cases of pelvic surgery where the laparoscope is able to enter, illuminate, and provide magnified views of spaces that are not generally in the direct line of sight for the surgeon.
Laparoscopy, however, is hindered by several limitations. One of these limitations is that tactile feedback of the internal anatomy is nearly eliminated when the surgeon cannot place a hand in the body cavity, limiting the identification of structures that are not visible within the peritoneal cavity, such as those that lie within the retroperitoneum and pelvis, which may have been otherwise recognized by feel. In addition, although the magnified view provided by laparoscopy offers excellent inspection of objects to the front of the camera, it drastically limits the field of view and does not allow visualization of the areas outside of the forward optical axis.
When vital anatomical structures are not found, or perhaps worse when they are misidentified, serious and even life threatening injury may occur. These complications include urinary tract injury, sexual or urinary dysfunction, infertility, and bleeding. Ureter injury, which is the most common intraoperative complication of pelvic surgery, occurs at a rate of about 1 to 10%. However, post-operative urinary and sexual dysfunction can occur at alarming rates, up to 100% in some studies, when resection is undertaken in the pelvis for cancer. In some rare instances, death may occur due to exsanguination from loss of orientation and inadvertent injury of the aorta, inferior vena cava, iliac, or gonadal vessels.
Augmented reality typically refers to the addition of computer-generated data to the real world in order to enhance situational awareness. Various approaches for visualization in image-guided interventions have been proposed to apply the concept of augmented reality and show anatomical structures on the laparoscope video. However, these systems remain crude in their anatomic modeling, alignment, and tracking. The majority of successful applications are in rigid settings and structures and use external motion tracking devices to track the laparoscope. More practical applications of simple two-dimensional image guided surgery are currently employed almost exclusively in maxillofacial and neurosurgery where the bony structures of the skull are used as landmarks for registration and reference. However, registration of images without the use of bony landmarks or placement of markers is complex. Non-rigid settings and deformable structures are encountered in laparoscopic abdominal surgery where external tracking becomes unreliable due to frequent occlusions.
From the above discussion, it can be appreciated that it would be desirable to have an improved augmented reality system and method for minimally invasive surgery procedures that do not rely upon rigid anatomical structures or external tracking devices.